Prior art is represented by other monitor calibrators that lack stability when attached to the glass surface of a cathode ray tube (CRT) commonly used for computer monitors. The lack of stability is due to the way the device is attached to the monitor, and the cantilever effect that gravity has on the device once mounted.
One example cited is the Xrite DPT 92. The Xrite device uses a single large suction cup that is mounted on the device to attach to the glass surface of the monitor. Since the single large suction cup is offset from the true center of gravity of the device, the device and others designed similarly will have a tendency to droop or rotate downward due to the effect of gravity. This drooping action causes the light detector and related optics to rotate out of the plane of the CRT or monitor. Once the device rotates out of the plane of the monitor, the device may result in poor performance or unwanted error.
Another type of monitor calibrator known as the sequel device attempts to overcome the problem of drooping by attaching multiple suction cups on the mounting side of the device. In this case, the suction cups adhere to the monitor to try and improve stability, however, there is also some degree of droop or rotation. In the case of this design, the multiple suction cups are mounted to one side of the device, but the suction cups are still offset to the true center of gravity of the device, causing droop or rotation error. In addition to droop or rotation, this approach also results in adding a level of non-repeatability in measurement.